Here’s an interesting idea that could explain some of the more puzzling features of our universe.
Cosmologists have long found evidence that the universe began in a big bang event and then expanded equally in all directions to become the cosmos we see today. They can see that distant galaxies are moving away from us, suggesting that the universe is expanding, and they can even see the echo of the big bang that caused this expansion.
That this echo seems evenly distributed around us has helped to back up the idea that we live in an ordinary part of the Universe that is more or less the same as every other part.
Neat and simple!
But in recent years, a number of strange observations have begun to make cosmologists think again. First, they’ve discovered that the universe is not just expanding but accelerating away form us. The evidence comes from observations of distant supernovas. And second, they’ve found that a closer examination of the echo of the big bang shows that it isn’t evenly distributed at all but stronger in some directions than in others, the so-called Axis of Evil.
Nobody has come up for a satisfactory explanation of these observations, which leaves physicists in a bind. Not least because the observations imply that the universe is not more or less the same everywhere, that there are preferred directions and that the laws of physics may be different elsewhere in ways that are hard ot imagine and even more difficult to measure.
That’s not so neat and not so simple.
Today, however, Edmund Schluessel at Cardiff University in Wales says that gravitational waves can explain all these observations. These are waves in the fabric of spacetime created by momentous events such as the collision of black holes and even the big bang itself.
Until now, cosmologists have considered only waves with relatively short wavelengths. But Schluessel’s idea is to imagine what the universe would look like if it contained much bigger waves with a wavelength of the order of the curvature of the cosmos itself, that’s some 10^10 light years. These would be waves left over from the big bang that continue to resonate slowly on a vast scale
Here’s the thing. Schluessel says these waves would distort the microwave back ground radiation in way that matches the preferred directions cosmologists see today. What’s more, it would also distort the light from distant objects in way that would make them look as if they were accelerating away.
Schluessel’s conclusion is that “Strong long-scale gravitational waves can explain cosmic acceleration within the context of general relativity without resorting to the assumption of exotic forms of matter such as quintessence.”
That’s impressive given the contorted models that others have come up with. Schluessel even makes predictions about what the next generation of telescopes are likely to see if his model is correct. In particular, he says that more comprehensive surveys of distant supernovas should reveal the imprint of the waves. In other words, the waves should make the universe look as if it is accelerating more quickly in some directions that in others.
Time will tell. But in the meantime, Schluessel’s model should give other cosmologists something to think about
Ref: arxiv.org/abs/1109.4315: Long-Wavelength Gravitational Waves And Cosmic Acceleration
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